1. Technical Field
This disclosure relates generally to controlling case length rates in material handling conveyors.
2. Description of Related Art
A singulator conveyor is an example of a conveyor that accepts clustered (overlapping, non-single file) case flow. A trash conveyor is another example. A singulator conveyor discharges the cases in a single file stream. A singulator conveyor works best when the case length rate (cumulative length of cases per unit time, which may be expressed in units of case feet per minute, or CFPM) of the incoming cases matches the case length rate of the outgoing cases. However this does not mean that the instantaneous incoming case length rate needs to match the instantaneous outgoing case length rate. To illustrate, a singulator conveyor must travel 24″ to induct two side-by-side 24″ long cases (48 case-inches) at the receiving end (two case-inches per conveyor-inch). Because it discharges cases in a single file stream, the singulator conveyor can only discharge 24 case-inches (one case-inch per conveyor-inch) during the same time period that it receives the 48 case inches. So there must be a period of time when the incoming rate is less than the maximum outgoing rate to allow recovery. For the best performance, the average incoming/outgoing case length rates are matched, averaged over a period of time, on a rolling basis.
When the average incoming case length rate exceeds the average outgoing case length rate capacity, i.e., overfeeding, there are excess cases which are overlapping. Overlapping cases must be recirculated, thereby reducing the efficiency of the singulator conveyor. Recirculated cases add to the incoming load on the singulator conveyor. When the average incoming case length rate is less than the average outgoing case length rate capacity of the singulator conveyor, i.e., underfeeding, case throughput is not maximized, and capacity goes unused. Reaching the maximum useful output capacity of a singulator conveyor requires that the average case feet rate delivered by the conveyor system upstream of the singulator conveyor match the outgoing average case length rate of the singulator conveyor.